I recently rebuilt the engine after a big overheat, on rebuild I had oil pressure on gauge and oil to the top end and turbo but no apparent flow at the big ends
Right. I am not one of our forum experts on this subject. So my comments would need verifying.
But as far as I know the main bearings get oil before the top end does. So it would appear that you have a blocked gallery or something. I have looked for a diagram but do not have one I am afraid. I think that @OldMav and @bambill would know the details of this, so hopefully one of them will see this.
Thanks so much I had to manually search thru the manual because i didnt know how it worked but I found the diagram that I needed and have built up a plan in my head on what I'm doing tomorrow.